1. Field of the Invention
The present invention relates to solid-state imaging elements and solid-state imaging devices, and particularly to a charge-coupled device (CCD) solid-state imaging element and a CCD solid-state imaging device that include a plurality of horizontal transfer registers.
2. Description of the Related Art
An existing CCD solid-state imaging element includes, on a semiconductor substrate, plural photosensors that are two-dimensionally arranged vertically and horizontally, plural vertical transfer registers provided adjacent to these photosensors, and a horizontal transfer register provided adjacent to one ends of these vertical transfer registers. In the CCD solid-state imaging element, signal charges arising from photoelectric conversion in the respective photosensors in response to light reception thereof are transferred by the vertical transfer registers and horizontal transfer register.
An output amplifying circuit is provided at the end terminal of the horizontal transfer register. The output amplifying circuit is configured to be capable of outputting the voltage corresponding to signal charges transferred from the horizontal transfer register, and outputs signal charges accumulated in the respective photosensors as a voltage signal.
Solid-state imaging devices including such solid-state imaging elements are demanded to have higher performance. Therefore, in solid-state imaging elements used in solid-state imaging devices, great importance has been attached to property improvements such as an increase in the number of pixels and an enhancement in the frame rate.
If the number of pixels in a solid-state imaging element is increased in particular, the number of photosensors formed on a semiconductor substrate is also increased and thus the frame rate is decreased. The frame rate decrease possibly leads to lowering of usability of the solid-state imaging device at the time of use thereof, such as difficulty in shortening of the imaging interval and setting a large maximum number of continuous shooting frames.
To address this, in recent years, methods in which plural horizontal transfer registers are disposed in parallel to each other have been employed for achievement of a larger number of pixels in a solid-state imaging element. Examples of the methods include a method in which signal charges on an odd-numbered horizontal line and signal charges on an even-numbered horizontal line are transferred by separate horizontal transfer registers, and a method in which signal charges on the same horizontal line are transferred by plural horizontal transfer registers.
FIG. 13 is a schematic diagram of a solid-state imaging element 100a in which signal charges of plural horizontal lines are transferred by separate horizontal transfer registers. This solid-state imaging element 100a includes a first horizontal transfer register 110a that horizontally transfers signal charges transferred from plural vertical transfer registers 101a and a second horizontal transfer register 111a that horizontally transfers signal charges transferred from the plural vertical transfer registers 101a via the first horizontal transfer register 110a. In the solid-state imaging element 100a, signal charges on an odd-numbered horizontal line and signal charges on an even-numbered horizontal line are simultaneously transferred by these separate horizontal transfer registers 110a and 111a so that the signal charges of two lines are read out within 1H (horizontal scanning period), to thereby achieve a higher frame rate (refer to e.g. Japanese Patent Laid-open No. Hei 6-105239).
FIG. 14 is a schematic diagram of a solid-state imaging element 100b in which signal charges on the same horizontal line are transferred by plural horizontal transfer registers. This solid-state imaging element 100b includes a first horizontal transfer register 110b that horizontally transfers signal charges transferred from vertical transfer registers 101b on odd-numbered vertical lines and a second horizontal transfer register 111b that horizontally transfers signal charges transferred from the vertical transfer registers 101b on even-numbered vertical lines via the first horizontal transfer register 110b. In the solid-state imaging element 100b, signal charges on odd-numbered vertical lines and signal charges on even-numbered vertical lines are simultaneously transferred by these separate horizontal transfer registers 110b and 111b so that the amount of signal charges horizontally transferred in 1 H by each of the horizontal transfer registers 110b and 111b is small, to thereby achieve a higher frame rate.